JP5730056B2 - Exhaust gas recirculation system for internal combustion engines - Google Patents

Description

  The present invention relates to an exhaust gas recirculation system for an internal combustion engine that recirculates part of the exhaust gas to an intake passage in an internal combustion engine equipped with a supercharger.

  2. Description of the Related Art Conventionally, for example, in an internal combustion engine mounted on a vehicle, an exhaust gas recirculation system that recirculates part of the exhaust gas to the intake passage is used in order to reduce air pollutants in the exhaust gas and improve fuel consumption. What you have is known. For example, in the one described in Patent Document 1, when an intake throttle valve is provided on the downstream side of the compressor of the turbocharger and exhaust gas is recirculated during low load operation, the pressure in the intake passage is reduced by closing the intake throttle valve. The differential pressure between the intake passage side and the exhaust passage side of the EGR passage connecting the upstream side of the turbine and the downstream side of the compressor is increased, and the exhaust gas is recirculated into the intake passage.

  In the above configuration, the differential pressure can be increased by closing the intake throttle valve, but depending on the operating state of the internal combustion engine, if the intake throttle valve is closed until the differential pressure is increased, the intake throttle valve The opening may be very small. In such a case, when the opening of the intake throttle valve is reduced, the intake throttle valve generates intake resistance, and the pumping loss increases.

  In view of such circumstances, if the exhaust gas is recirculated into the intake passage with the intake throttle valve opened, the intake air is compressed by the compressor from the pressure of the exhaust gas depending on the operating state of the internal combustion engine. The fresh air pressure becomes higher and the exhaust gas cannot be recirculated. That is, since the differential pressure does not occur and the pressure of the exhaust gas is lower than the pressure of fresh air, fresh air may flow into the exhaust passage through the EGR passage. In this case, when the fresh air reaches the catalyst, the atmosphere in the catalyst becomes more than the amount of oxygen necessary for purifying the exhaust gas, and the exhaust gas purification ability may be reduced.

Japanese Patent Laid-Open No. 10-266866

  Therefore, the present invention pays attention to the above points and recirculates a part of the exhaust gas even in the operating region of the internal combustion engine in which the pressure of the fresh air that becomes the compressed intake air exceeds the pressure of the exhaust gas, thereby improving the fuel efficiency. The purpose is to improve the torque by improving and suppressing knocking.

That is, an exhaust gas recirculation system for an internal combustion engine according to the present invention has a supercharger for supercharging intake air and an exhaust gas recirculation line connected downstream of the compressor in the intake passage, and a part of the exhaust gas. the a exhaust gas recirculation system of an internal combustion engine having an exhaust gas recirculation device for recirculating to the intake passage, and storing the gas in a given volume communicating with the pipe portion and the tube portion connected downstream of the compressor definitive intake passage In the operating region where the intake pressure downstream of the compressor may be higher than the exhaust pressure in a state where a part of the exhaust gas is recirculated to the intake passage by the exhaust gas recirculation device, a phase different from the intake pulsation a phase changing means for reducing than exhaust pressure to intake pressure of the compressor downstream by interfering with output to intake pulsation of the pulsation of the communication with the phase changing means and the intake passage And Gosuru off valve, a reflux detecting means for detecting a refluxing the exhaust gas by the exhaust gas recirculation device, the intake pressure of the compressor downstream in a state where the exhaust gas recirculation system is recirculating part of exhaust gas to the intake passage In an operating region where the pressure may be higher than the exhaust pressure, the valve control means for opening the on-off valve and operating the phase changing means is provided.

  According to such a configuration, when the operating state in which a part of the exhaust gas is recirculated to the intake passage by the exhaust gas recirculation device is detected by the recirculation detection means, the valve control means opens the on-off valve to open the intake passage. The suction air flows into and out of the pipe portion of the phase change means, acts on the gas in the container, and the gas in the container acts on the suction air in the suction passage with a phase that is ½ wavelength different from the pulsation of the suction air. As a result, the pressure of the intake air can be made lower than the pressure of the exhaust gas.

  The present invention is configured as described above, and in the operating state in which the exhaust gas recirculation device is operating, even in the operating state in which the pressure of the intake air exceeds the pressure of the exhaust gas, It is possible to prevent fresh air from flowing back into the exhaust passage via the exhaust gas recirculation device. Therefore, a larger amount of exhaust gas can be recirculated to the intake passage, fuel efficiency can be improved, and torque can be improved by suppressing knocking. In addition, since the exhaust gas whose air-fuel ratio has changed to the lean side due to fresh air can be suppressed from flowing into the catalyst, it is possible to prevent the exhaust gas purification performance from being deteriorated.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing of the engine of embodiment of this invention. The graph which shows the change of the intake pressure and exhaust pressure for demonstrating the effect | action of the embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The engine 100 has a two-cylinder 360 ° phase, and includes a cylinder 1, an intake passage 2 for supplying intake air to each cylinder 1, an exhaust passage 3 for discharging exhaust gas, and an exhaust passage 3. An exhaust turbine turbocharger 4 having a turbine 4a and a compressor 4b disposed in the intake passage 2 is basically provided.

  In addition to the compressor 4b, the intake passage 2 includes an air cleaner 7, an air flow meter 6, an intake throttle valve 8, an intercooler 9, and an electronically controlled throttle valve (hereinafter referred to as an electronic throttle valve) 10 from the upstream side of the intake passage 2. It arranges in this order toward the downstream. That is, the air flow meter 6 for detecting the air flow rate is disposed downstream of the air cleaner 7 and thus upstream of the intake throttle valve 8. Thus, since the air flow meter 6, the intake throttle valve 8, the intercooler 9, and the electronic throttle valve 10 are arranged downstream of the air cleaner 7, the intake passage 2 has a long overall length.

  Further, in the intake passage 2 between the air flow meter 6 and the intake throttle valve 8, an intake bypass passage 24a communicating upstream of the throttle valve 10 and downstream of the intercooler 9 and an intake bypass valve 24b opening and closing the intake bypass passage 24a are provided. A supercharging pressure bypass mechanism 24 is provided.

  A spark plug 15 and a fuel injection valve 16 are attached to each cylinder 1. Fuel is supplied to the fuel injection valve 16 from a high-pressure fuel pump 18 via a delivery pipe 17.

In the exhaust passage 3, in addition to the turbine 4a, an air-fuel ratio sensor 20, a three-way catalyst 21, and a rear O ₂ sensor 22 are arranged in this order from upstream to downstream of the exhaust passage 3. That is, the air-fuel ratio sensor 20 is disposed downstream of the turbine 5, the three-way catalyst 21 is disposed downstream of the air-fuel ratio sensor 20, and the rear O ₂ sensor 22 is disposed downstream of the three-way catalyst 21. The air-fuel ratio sensor 20 and the rear O ₂ sensor 22 are electrically connected to an electronic control device 33 described later.

  As the turbocharger 4, those well-known in this field can be applied. In order to control the supercharging pressure, the turbocharger 4 includes an exhaust bypass passage 23 a that allows communication between the upstream side and the downstream side of the turbine 4 a. A waste gate valve 23b for opening and closing the bypass passage 23a is provided.

  The engine 100 is a so-called high-pressure loop type exhaust gas recirculation device (hereinafter referred to as “high pressure loop”) for mixing exhaust gas into fresh air flowing into the intake passage 2 via the air cleaner 7 between the intake passage 2 and the exhaust passage 3. , Referred to as an EGR device) 25. An exhaust gas recirculation conduit (hereinafter referred to as an EGR conduit) 26 that communicates the intake passage 2 and the exhaust passage 3, and a part of the exhaust gas that is provided in the EGR conduit 26 and passes through the EGR conduit 26, that is, And an exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 27 for controlling the amount of EGR gas. One end of the EGR pipe 26 is connected to the intake manifold 2 a constituting the intake passage 2, and the other end is connected to the exhaust manifold 3 a constituting the exhaust passage 3.

  In addition to the EGR device 25, a pipe 40 communicating with the intake passage 2 and a container capable of storing a predetermined volume of gas downstream of the electronic throttle valve 10 and upstream of the intake manifold 2a. And a phase change means 42 for changing the phase of the intake pulsation, and an opening / closing valve 43 provided between the intake passage 2 and the pipe portion 40 for controlling the communication state between the phase change means 42 and the intake passage 2. It is. The phase changing means 42 is a resonator that uses the so-called Helmholtz resonance principle. While the opening / closing valve 43 is open, the phase changing means 42 communicates with the intake passage 2 at the upstream position of the intake manifold 2a while the pipe portion 40 communicates with the intake air pulsation phase and half of the intake air pulsation phase based on the Helmholtz resonance principle. Generates pulsations with different wavelengths. Thereby, the pulsation of intake air is reduced.

  The phase change means 42 described above, the recirculation detection means and valve control means described later, and the EGR device 25 constitute an exhaust gas recirculation system.

The electronic control device 33 is a computer system including a processor 33a, a memory 33b, an input interface 33c, an output interface 33d, and the like. The input interface 33c includes an air flow rate signal a output from the air flow meter 6, a vehicle speed signal b output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal c output from a rotation speed sensor that detects the engine speed, A throttle opening signal d output from a throttle sensor that detects the opening of the throttle valve 10, that is, a throttle opening, is attached upstream of the intake manifold 2 a to a surge tank (not shown) integral with the intake manifold 2 a and intake pressure An intake pressure signal e output from the intake pressure sensor for detecting the coolant, a water temperature signal f output from the water temperature sensor for detecting the coolant temperature, a first air-fuel ratio signal g output from the air-fuel ratio sensor 20, and a rear O ₂ sensor. The output second air-fuel ratio signal h or the like is input. From the output interface 33d, the throttle valve opening signal k for the intake throttle valve 8, the valve drive signal m for the throttle valve 10, the EGR valve opening signal n for the EGR valve 27, and the fuel injection valve 15 are supplied. On the other hand, the fuel injection signal o, the ignition signal p to the ignition plug 16, the opening / closing signal q to the opening / closing valve 43, and the like are output.

  The electronic control device 33 also functions as a reflux detection unit and a valve control unit. The recirculation detection means detects that a part of the exhaust gas is recirculated to the intake passage 2 by the EGR device 25. In this embodiment, the EGR valve opening degree of the EGR valve 27 of the EGR device 25 is detected. The valve opening degree of the EGR valve 27 is estimated based on the signal s, and it is detected from the valve opening degree that the EGR device 25 is recirculating a part of the exhaust gas. Then, by detecting this reflux, the electronic control unit 33 outputs an opening / closing signal q for opening the valve to the opening / closing valve 43. Therefore, the electronic control unit 33 functions as a reflux detection unit and a valve control unit.

In such a configuration, as shown in FIG. 2, fresh air is generated by the turbocharger 4 in the low-rotation medium-high load operation region in which a part of the exhaust gas is recirculated to the intake passage 2 by the EGR device 25 according to the operation state. Therefore, the pressure of the intake air, that is, the intake pressure, may be higher than the pressure of the exhaust gas, that is, the exhaust pressure (sections A and B in the figure). In this case, when the recirculation detection means detects recirculation of the exhaust gas by the EGR device 25 and the valve control means opens the on-off valve 43, the phase changing means is activated for the pulsation of the intake pressure, and the pulsation of the intake pressure The pulsation is output from the phase changing means at different phases. That is, the gas in the container 41 is repeatedly compressed and expanded by the intake air flowing into and out of the pipe portion 40 of the phase changing means 42, and vibrates at a phase different from the pulsation of the intake pressure. As a result, the pulsation of the intake pressure is interfered, and the intake pressure is reduced to be lower than the exhaust pressure.

  As a result, since the exhaust pressure exceeds the intake pressure in the intake manifold 2a, a part of the exhaust gas is mixed with the intake air via the EGR pipe line 26 and the EGR valve 27 of the EGR device 25. Therefore, even in such an operating state where the intake pressure exceeds the exhaust pressure, the exhaust gas can be recirculated, and fuel efficiency and torque can be improved. Further, since the exhaust pressure is higher than the intake pressure, it is possible to suppress the intake air from being blown into the exhaust manifold 3a via the EGR pipe line 26. For this reason, it can suppress that the oxygen concentration of exhaust gas becomes high, and can suppress that the air fuel ratio in the three-way catalyst 21 becomes lean. Therefore, it is possible to prevent the exhaust gas purification performance of the three-way catalyst 21 from being deteriorated.

  As described above, when the on-off valve 43 is open, the electronic throttle valve 10 is fully opened or fully closed, and the EGR valve 27 is controlled to be closed. When the exhaust gas is not recirculated by the device 25, the recirculation detection means detects that the exhaust gas is not recirculated based on the opening degree of the EGR valve 27. As a result, the valve control means outputs an opening / closing signal q for closing the opening / closing valve 43 after a predetermined delay time. The predetermined delay time is set to a sufficient time required to close the EGR valve 27 in order to complete the exhaust gas recirculation in a state where the exhaust pressure exceeds the intake pressure. In this way, the opening / closing signal q for closing the opening / closing valve 43 is output and the opening / closing valve 43 is closed, so that fresh air is surely prevented from being blown into the exhaust passage 3. Therefore, as described above, it is possible to prevent the exhaust gas purification performance of the three-way catalyst 21 from being deteriorated.

  The present invention is not limited to the above embodiment.

  As the recirculation detection means, the exhaust gas from the EGR device 25 is detected by detecting that the required EGR rate or the required EGR amount calculated based on the engine speed and the load is equal to or greater than a predetermined EGR rate or EGR amount. It is also possible to detect the reflux of water.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Examples of utilization of the present invention include gasoline and diesel engines that are equipped with a turbocharger and have a large intake pulsation such as two or three cylinders.

DESCRIPTION OF SYMBOLS 2 ... Intake passage 3 ... Exhaust passage 4 ... Turbocharger 25 ... Exhaust gas recirculation device 33 ... Electronic control unit 40 ... Pipe part 41 ... Container 42 ... Phase change means 43 ... Open / close valve

Claims (1)

Internal combustion engine having an exhaust gas recirculation device for recirculating intake air in the intake passage part of the exhaust gas has an exhaust gas recirculation line which connects the downstream of the compressor in the turbocharger and the intake passage for supercharging Exhaust gas recirculation system of
It becomes a gas of a predetermined volume communicating with the pipe portion and the tube portion connected to the downstream of the definitive intake passage compressor from a container capable of storing a state that recirculating part of exhaust gas into the intake passage by an exhaust gas recirculation system In the operating region where the intake air pressure downstream of the compressor may be higher than the exhaust pressure, a phase that outputs a pulsation with a phase different from the intake pulsation and interferes with the intake pulsation, thereby reducing the intake pressure downstream of the compressor below the exhaust pressure. Change means,
An on-off valve for controlling the communication state between the phase changing means and the intake passage;
Recirculation detection means for detecting recirculation of exhaust gas by the exhaust gas recirculation device;
In the operating region where the intake pressure downstream of the compressor may be higher than the exhaust pressure while part of the exhaust gas is recirculated to the intake passage by the exhaust gas recirculation device, the on- off valve is opened to operate the phase change means An exhaust gas recirculation system for an internal combustion engine, comprising:

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